1. Field of the Invention
The present invention relates to a wiring board with a fine wiring pattern adapted for a circuit device mounted with, e.g., semiconductive elements and chip parts, and manufacturing method thereof.
2. Description of the Related Art
Generally, a wiring board (wiring circuit substrate) is conventionally manufactured by a method where a copper foil, which is adhered to the surface of an insulating plate such as a glass epoxy resin plate with an adhesive, is subjected to photoengraving process (PEP) to form a desired wiring pattern. Further, a board with multi-layer wiring, which is manufactured for highly densifying a wiring and compacting a wiring board, has been known. These multi-layer wiring boards are manufactured by a method where a plurality of the above mentioned insulating plates with a desired wiring pattern are laminated, for example, via an adhesive layer and then processed under heat and pressure to be integrated together; and thereafter holes, which continuously connect between the desired wiring patterns, are perforated in the direction of the thickness such that the desired wiring patterns are electrically connected, for example, by an electroplated layer, via these perforated holes.
In the above method for manufacturing a wiring board, the following methods for the formation of a wiring pattern have also been known; One method is that instead of a copper foil, a metal layer formed by vapor deposition or sputtering method is subjected to photoengraving process to form a pattern. The other method is that chemical plating or electroplating is further conducted on the previously mentioned pattern to reduce the wiring resistance.
In any wiring boards manufactured by the above methods, only conductors of particular parts (particular areas) of a wiring pattern are formed independently of each other so as to electrically connect to electric parts to be mounted on the surface. An electric examination (open check) is conducted by the use of a special tool with standing needle-shape terminals which respectively correspond to exposed conductive parts independent of each other. For example, as shown in FIG. 1, a wiring board (wiring circuit substrate) 1 is placed on a special stand 2, a special tool 3 (generally called as a probe card) with erected needle-shape terminals 3a intimately contacts at the position corresponding to exposed conductive parts formed independently of each other on the surface of the wiring board 1, and then an electric examination is conducted by a tester 4.
However, in the above wiring board, there are following problems with respect to the manufacturing method thereof. First, in the case where the conductive metallic layer (foil) is subjected to selective etching to form a predetermined wiring pattern, a series of processes called "the photoengraving process", that is, the formation of a photoresist film, selective exposure with a exposure mask (accuracy for the position of an exposure mask is particularly important), development and selective etching are required. Particularly, in the case of a multi-layer wiring board, during or after the laminating process, it is necessary to form through or non-through holes for electric connection between desired wiring pattern layers and to make conductive the holes. As a result, processes become further complicated and facilities for manufacturing or processing become larger. Second, in practicing a manufactured wiring board, an examination for the function thereof as a required electric circuit is necessary. However, as described above, this electric examination requires the use of a tool in which terminal positions for each wiring pattern are designed. Thus, at each time of changing a wiring pattern, the tool must be designed, formed and selected. In addition, in the examination process, it takes much time to set the wiring board 1 and tool 3 as shown in FIG. 1 and the examination itself is complicated. Thus, as a wiring pattern becomes of multi-layer structure or finer, these problems become greater. In other words, the electric examination becomes considerably complicated and further the probability of connection defects increases, resulting in lowering yield in a multi-layer wiring board and reliability of a product.